The present invention relates to a boot control method to be used for a computer system having a redundant computer structure to boot up a computer via a storage area network (SAN) by use of a software image stored in a device adapted to the SCSI-protocol.
Fibre Channel has become a mainstream standard in recent years for the connection of storage devices in a storage area network (SAN). However, implementation of Fibre Channel connection requires construction of a new independent network even in an environment in which a LAN (Local Area Network) has already been constructed using Ethernet (registered trademark) cables. Further, costs for introducing interfaces for Fibre Channel (Host Bus Adapters) and Fibre Channel switches are extremely high compared to those for Ethernet.
Under such circumstances, SANs employing Gigabit Ethernet are recently attracting much attention. This connection method is extremely cost effective since Gigabit Ethernet has become widespread enough and many people have already purchased interfaces for Gigabit Ethernet (hereinafter referred to also as “Ethernet controllers”) and constructed LAN environments. Software held in the Ethernet controller boots up an operating system stored in a storage device (iSCSI attached device) which is connected to the Ethernet controller via an Ethernet network.
In a computer system in which booting of a computer from a SAN environment, connected to the computer via a network, is implemented, data stored in logical units in a RAID device (in which operating systems of separate computers have been installed respectively) have to be protected. For this purpose, a RAID device is equipped with a security function that prohibits each computer from accessing a logical unit of the RAID device other than a corresponding logical unit in which the operating system for the computer has been installed. The security function generally employs unique identification information which has been assigned to a network port of each computer. Specifically, the logical unit in which the operating system for a computer has been installed is associated with the unique identification information assigned to the network port of the computer, and only the network port having the unique identification information is permitted to access the logical unit.
Thus, when a redundant structure, i.e. having an active computer and a standby computer, is employed for a computer system in which the booting of a computer is carried out using a software image via a network, the unique identification information assigned to the network port of the active computer differs from that assigned to the network port of the standby computer, and thus it is impossible to let the standby computer take over and directly use the software image including the operating system by switching the network connection from the active computer to the standby computer. In this case, settings of the security function on the RAID device's side have to be changed by means of SAN management software or manual operation. The technology mentioned above has been elaborated on in JP-A-2007-94611 and JP-A-2002-149599, for example.